(a) Field of the Invention
The present invention relates to a method of bonding with a silver paste. More specifically, the present invention relates to a method of bonding with a silver paste to bond a semiconductor device.
(b) Description of the Related Art
Following the recent trend of appliances becoming larger and having a larger capacity, the need for power semiconductor devices having a high breakdown voltage with a high current and high-speed switching is increasing. Of these, silicon carbide (SiC) semiconductor devices have a wider band gap than existing silicon (Si) semiconductor devices, and thus implement stable semiconductor characteristics even at a high temperature.
However, it is necessary to apply stable packaging materials even at a high temperature in order to obtain the effect of high-temperature operation. Particularly, current solder used to bond semiconductor devices has a melting point of lower than 230□, and thus cannot be utilized at a bonding temperature of 250□ at which silicon carbide semiconductor devices are eventually operated.
In order to replace the current solder, high-temperature solder or the like containing gold (Au) has recently been suggested as an alternative. However, the high-temperature solder or the like is expensive and has inferior properties such as joining strength.
In addition, a method of sintering and joining silver (Ag) nano-particles has been suggested as a method for high-temperature bonding, but a long process at a high temperature is needed, resulting in deterioration in device characteristics. A paste containing a mediator material such as glass frit has been formed to activate sintering between large-sized silver particles, but residual glass may cause an increase in resistance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. addition, the joining is conducted using the silver paste which contains the silver particles and includes the core parts made of plate-shaped silver and the coating parts coated on surfaces of the core parts and made of indium, thereby minimizing the void distribution in the bonding layer.